This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A FAD-containing mammalian apoptosis inducing factor (AIF) is a phylogenetically old caspase-independent death effector that normally resides in the mitochondrial intermembrane space but upon apoptosis induction translocates to the nucleus and triggers chromatin condensation and large scale DNA fragmentation. Although there is strong evidence that AIF is linked to free radical homeostasis and oxidative stress, neither physiological function nor mechanism of apoptosis induced by this protein is known. To date, only the crystal structures of truncated, refolded forms of apoptogenic AIF are available. We found that refolding and truncation significantly perturb the redox properties of the flavoprotein. Thus, obtaining structural information on naturally folded, ?healthy? form of AIF is vital for understanding structure/function relationships and the physiological role of the protein in mitochondria. We obtained well-diffracting crystals of the naturally folded catalytic domain of AIF (residues 77-612) but owing to large cell dimensions the current resolution of the x-ray model is limited to 3.2 [unreadable], the detector size limit. We aim to extend the resolution by collecting the synchrotron data with the 2-theta angle set to 10-20[unreadable].